Inductor for high-frequency induction heating



INDUCTOR FOR HIGH-FREQUENCY INDUCTION HEATING.

Filed March 1.2, 1945 N. B. STEVENS ET AL Dec. 14, 1948.

2 sheets-sheet 1 IN VEN TOR. NELsoA/B. STE vE/vs. PASQUALE 1?.CAPOLONGO.

ATTORNEYS.

Dec. 14, 1948.. l N. B. STEVENS ET AL INDUCTOR FOR HIGH-FREQUENCY INDUCTION HEATING 2 Sheets-Sheet 2 Filed March 12, 1945 IN V N TOR. NE. 60 ALE. TEl/ENS. BPfjSQU/ILER C4 01. o/vao.

A TTORNEVJ.

Patented Dec. 14, 1948 INDUCTOR FOR HIGH-FREQUENCY INDUCTION HEATING Nelson B. Stevens, Woodhaven, and Pasquale R.

Capolongo, New York, N. Y., assignors to Induction Heating Corp., New York, N. Y., a corporation of New York Application March 12, 1945, Serial No. 582,264

4 Claims. (Cl. 219-47) This invention relates to inductors for high frequency induction heating purposes.

In high frequency induction heating it is common practice to provide an inductor or coil having a single turn for surrounding an object to be heated in spaced relation thereto and with close inductive coupling therewith. For example, several forms of such inductors are disclosed in the patent to Paul E. Dravneek 2,353,130, granted July 11, 1944. Such inductors may be formed with one or more apertures depending upon the number of work pieces to be heated at one time, and the structure is adapted to be rigidly and substantially permanently mounted in conjunction with terminal connections for a source of high frequency current and also connections for circulating cooling water through the inductor to prevent the same from becoming heated. In the production and heat treating of large numbers of like objects, inductors such as shown in said patent have proven highly successful. However, once the equipment is built and set up to heat-treat objects of a certain shape and size, modifications cannot be easily or quickly made to accommodate objects of other sizes or shapes. It has generally been necessary to construct a special inductor having the proper dimensions and other characteristics for each type of work to be treated, and in shifting from one job to another the inductors of one form have to be disconnected from the supporting structure and from the source of power and water connections so as to be able to replace the whole inductor structure by another one of appropriate design.

The present invention provides an improved inductor construction comprising a frame member having cooling fluid and electrical connections adapted to remain permanently in position, together with any necessary supporting structure, and such frame member is constructed to receive readily interchangeable and replaceable adaptor members or inserts having apertures of shapes preselected for appropriate close inductive coupling with Work pieces of difierent shapes or sizes. Thus, after finishing one job, the induction heating machine may be quickly prepared for another type of job merely by removing and replacing such adaptor means and without the necessity of disconnecting the electrical and water circuit connections or any of the supporting structure necessary for the inductor.

In accordance with this invention, the cooling fluid conduits for the inductor may be all located within the frame portion which may be of a standardized and inexpensive design and does not have to be altered to suit work pieces of various shapes and sizes. Also, since the adaptor means may be shaped and constructed independently of the parts of the inductor which include the terminals and cooling fluid conduits, it will be apparent that adaptors of numerous shapes may be made easily, quickly and inexpensively without special tools.

Various further and more specific objects, features and advantages of the invention will appear from the detailed description given below taken in connection with the accompanying drawings which form a part of this specification and illustrate merely by Way of example, certain preferred forms of the invention. The invention consists in such novel features, arrangements and combinations of parts as may be shown and described in connection with the apparatus herein disclosed.

In the drawings:

Fig. 1 is a plan view of a preferred form of inductor for heating a single work piece;

Figs. 2-6 inclusive are sectional views of several forms of adaptor members suitable for use in the device of Fig. 1;

Figs. 7-9 inclusive are plan views of adaptors also suitable for use in the device of Fig. v1;

Fig. 10 is a plan View of an inductor made according to a preferred embodiment of the inven tion and of a type adapted for simultaneously heating a plurality of objects;

Fig. 11 is a vertical sectional View of the device of Fig. 10 and showing the device as mounted in connection with the terminals of a high frequency transformer; and

Fig. 12 is a sectional view taken substantially along line l2l2 of Fig. 11.

Referring now to Fig. 1 in further detail, the inductor there shown may comprise a ring-like frame portion I5 formed with a narrow gap l6 at one side, terminal connection and supporting members as at IT and [8 being secured as by brazing at the respective sides of said gap. The members [7 and i8 may be supported respectively by terminal lugs as at l9 and 29 of the same type for example, as disclosed in the above-mentioned Dravneek patent. Cooling fluid connections may be provided as at El, 22 and the members [1, I5 and it may be formed with communicating cavities as at l1, l5 and H3 whereby the cooling fluid may enter for example through connection 2| and pass around the inductor back to connection 22. If desired, the cavity 15' may be provided by way of a sheet metal tube surround- 3 ing and brazed to the periphery of frame member 15.

It will be noted that the frame member I5 is formed with a central aperture as at adapted to receive the removable and replaceable adaptors or inserts,-one of which is shown at 26 in Fig.1. The adapter 26 for example is formed with a central circular aperture 2'! for receiving a Work piece of circular outline. One side of this adaptor is slotted as at 28 in alignment with .the slot. 16, so that the adaptor will not short-circuit the terminal connections. As shown in Fig. 1, the adaptor may be securedin place. asLby screws 30 located at spaced points around-the outer periphery of the adaptor and adjacent the inner periphery of the frame.

As shown in Figs. 2-5, the adaptors'may-preferably be formed with peripheral fiangesas at 3 l, or, stated in another way, the lower peripheral edges of the adaptors may be recessed as at 32. It will beunderstoodthat the-inner wallsof the. aperture 25 in theinductor frame-may be The adaptorshown in section in'Fig. 2 is similar to the one shown-in plan view in Fig. 1 except that a smaller central aperture as at 33 is provided to accommodate a smaller work piece. The adapter of Fig. 3 is also the sameexcept-that a larger central aperture 34 is'provided. *In'the adaptorof Fig. 4 a central aperture -35 is provided: having downwardly and outwardly tapered side walls for accommodating, for example; a work piece having a generally conical'surface. The adaptor of Fig. 5 has a central aperture 36, the walls of which are formed at the midportion withan annular cavity 37. With arr-aperture of this shape, for example if the work piece therein is of cylindrical-shape, two spaced annular areas thereon may be heated, viz., areas which come into close inductive coupling with the portions of the wall surfaces of-apertures-36 which are above and below the channel 31.

In Fig.6 an adaptor is shown having an-aperture 38 whichis tapered'inwardly and downwardly, at least'part way. From :the sectional views of Figs. 2-6 it will be noted that the adaptors-may be formed of plateelike material of varying thickness, depending uponhow far it is desired to have the heated area extend axially along the work piece. ,Thatis if only a narrow heated band isrequired, then a 'relatively thin adaptor plate may be selected. On the other hand, if a wide band is to beheated on the work piece, one may'select an adaptor formed of a relatively thick plate, and regardless of the thickness of the adaptor plate,*with-in reasonable limits, the same inductor frame or ring of standardized construction maybeused therewith.

Fig. 7 shows in plan View an adaptor substantially like that shown in section in Fig. 3. Fig 8 shows in plan viewan adoptor having an. aperture 4B of square shape to receive a work piece of square cross section. As shown inithis figure,

the metal adjacent the vertices of the angles at the corners. ofthis aperture is cutaway as. at M for a short distance. The purpose of this is to avoid excessive concentration of the. magnetic flux in the work piece immediately adjacent corners that excessive heating and injury of the corners of the workpiece may occur. On the other hand, by forming the cut-out portion-s as at H, the heating of the metal around the corner portions -and elsewhere adjacent the periphery -=of the-inductor aperture may be made substantially uniform. It will be understood that similar principles may be followed as indicated by Fig. 8

in-constructing adaptors having apertures of :other :polygonal shapes.

In Fig. 9 an adaptor with an aperture #2 of hexagonal shape is shown.

.Since the angles of this aperture are not so abrupt, the cut-out portion-s as at 4| of Fig. 8 maybe omitted here if desired.

Referring now to the construction of Figs.

ill-12, a rectangular plate-like frame member is here shown'formed' with a series of openings as at 5!, each of which corresponds in function to the'opening or aperture -25 of Fig. 1. Semiannular adaptor'plate members as-at 52 are securedas by screws 53 in each of the apertures 5!. Oertainprinciples of construction of this form of inductor-may be the same-as or" theT form "of inductor disclosed inconnection with-Fig. 1 of-the -above-mentioned Dravneek patent. Thai is,';inorder to form a circuit around all of the apertures collectively, the body'portion of the "inductor is formed with a 'T-shaped slot with or supports.

slots or notches as :atf58-may be formed, open- 4Q.

curing more "uniform 'heating "of the objects within said apertures'in amanner morefully versely, extending slots 'as at 59.

slotportionsas at 54,65, '56- along the cross portion of the T, serving to interconnect each adjacent'pair of apertures, and a slotportion'as at Ell-serving toseparate the terminal connections Also ateach end of the device,

ing into'the end apertures "forpurposes of seexplainedinsaidDravneek patent. in the exampleshown in Figs. 10 and 12, the outer ends 'of the" notches "or slots58' may open into trans- With these .'transverseslots'59, a uniform heating'effect may be obtained around within the adjacent :work

"piece apertures Without makingthenotches'SB as'long or extended aswould be desirable for "such uniform heating effectin the absence of the adjacent work piece apertures, is substantially'the equivalent of that obtainable ifthere were another work piece aperture in place of each slot/59. Yet this effect is obtainedwithout the inductance increase which would occur if the device were equipped with empty or unused apertures of circular form at theeends.

The device ofFigs. 10-12 may be tormed with a terminal connection and supporting structure including coolingfiuid inletand outlet connec- .tions,'the same or equivalent to' that .described in connection with'Fig. 1. .In'Fig.lithe-terminal and supporting structure is :shown. as applied to the secondary terminals .,-at..60..of a1high irequency transformer 6! serving. as the .sourceof supply of current forithe inductor.

"As isbest shown inFig. 10,.thev peripheral pertime 'of" the frame orplate member 50 may be formed with a cooling fluid cavity as indicated by dotted lines at 62. This cavity may for example be formed by drilling holes inwardly from the edge surfaces at the corners of the plate and then plugging the undesired drill hole openings, for example, with pieces of metal plugs brazed in place. With the fluid cavity formed in this way the construction is rigid,'permanent and relatively inexpensive, and externally the frame plate presents the appearance ofa solid plate member with unobstructed smooth external surfaces which may be easily cleaned.

As in the case of the structure of Fig. 1, it will be understood that the insert or adaptor members in Figs. 12 may be shaped internally in various ways depending upon the dimensions and shape of the objects to be heated. Any of the shapes of adaptors shown in Figs. 2-9 for example.'may be used in the device of Fig. 10 except that it will be understood that because of the necessity of interconnecting adjacent openings by slots as in Fig. 10, the adaptors for this device have to be formed of two parts separated by a narrow slot or gap at each side. Also as shown in Fig. 12, the adaptors may be formed at their peripheries with flanges and/or recesses as in the case of the construction of Fig. 1 or otherwise formed in a manner such that the walls of the apertures 5| will be more restricted at the lower side of the frame plate to thus afford support against which the screws 53 may retain the adaptors in firm reliable contact for good heat and electrical conduction purposes uniformly around the peripheries of the adaptors except for the gaps.

It will be apparent that the invention provides a construction in which the main frame parts of the inductors, including the electrical connections and cooling fluid connections may be maintained in permanent assembly with the remainder of the high frequency induction heating apparatus. Yet by the use of the interchangeable inserts or adaptors, any one or more of the work piece apertures may be quickly modified to accommodate work pieces of a variety of shapes and dimensions. Also it will be apparent that if any of the adaptors should become injured, as for example due to arcing effects, same may be quickly replaced with no more than a moments interruption of operations. Also if the adaptors of these slotted gap regions should become clogged with flux or brazing material or need cleaning for other reasons, they may be quickly removed and more readiy and effectively cleaned than may be the constructions heretofore available.

Since the inductor frame remains stationary, the interchanging of the inserts will not affect the alignment of the work piece apertures in the frame relative to the axes of fixtures, etc. for supporting the work pieces. The invention also provides a construction convenient for experimental, trial and laboratory work. For example, if it is desired to make a series of tests as to the heating effect on a given work piece using apertures of different sizes or configurations, such tests may be made in rapid succession using a single standardized inductor frame. In that case, if desired, instead of attaching the inserts by ordinary screws, it will be understood that wing nuts, thumb screws or quick-detachable locking means might be provided.

While the invention has been described in detail with respect to certain preferred example, it will be understood by those skilled in the art after understanding the invention, that various changes and further modifications may be made without departin from the spirit and scope of the invention, and it is intended therefore in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to'be secured by Letters Patent is:

J 1. An inductor for high frequency induction heating, comprising a pair of adjacent supporting and terminal connection members, a ring-like frame portion fixed thereon for completing a circuit connection therewith, said members and frame portion being formed with cavities for circulation of cooling fluid therethrough, and readily removable and replaceable plate-like adaptor means mounted to extend over the space within said frame portion, and formed with a central aperture of size and shape preselected to receive the object to be heated with close inductive coupling therewith, the periphery of said adaptor means and the interior of said ring member being formed with complementary interengaging flanges, and said adaptor means and frame portion being correspondingly slotted adjacent said terminal connections to avoid short-circuiting same, the said interengaging flanges providing effective electrical and heat conducting contact therebetween substantially continuously around the frame portion except at the slot.

2. An inductor for high frequency induction heating, comprising a conductive frame portion formed with at least one aperture, the walls of which are adapted to extend substantially around at least one object to be heated, in a widely spaced relation thereto, a narrow gap being formed in at least one side of said frame portion and opening into said aperture, means connected respectively at each side of said gap for applying high frequency current, said means and said portion being formed with a cooling fluid cavity therein extending from one current connection around said frame portion to the other current connection, removable disc-like conductor means formed with a smaller aperture of size and shape preselected to receive the object to be heated with close inductive coupling therewith, said latter means also being formed with a narow gap adapted for alignment with said first mentioned gap, the inner aperture walls of said frame portion and the peripheral edges of said removable conductor means respectively being formed with overlapping fiange surfaces, a plurality of screw means being provided for removably retaining said removable conductor means in position on said frame portion with said overlapping surfaces in effective electrical and heat conducting contact substantially continuously around the aperture borders of the frame portion.

3. An inductor for high frequency induction heating comprising a conductive frame formed with a plurality of apertures each adapted to receive a work piece in widely spaced relation with the aperture wall-s, said frame being formed with narrow slots including slots interconnecting each adjacent pair of apertures and all arranged whereby a current path in the frame is provided extending around all of the apertures, said frame also being formed with a cavity for circulating cooling fluid along said path, and pairs of semicircular plate-like complementary adaptor members which are removably and replaceably fixed to extend over the space within each of said apertures, each pair being separated by narrow gaps forming continuations of said interconnecting slots, and each pair of adaptor members serving jointly to form a smaller aperture of size and 

